Concerns regarding the Conservation of
Functional Horological Objects

This document is a response to a query in the Conservation DistList,
Conservation DistList, Instance: 16:46, Friday, January 31, 2003,
subject "Tall case clock". This is a start in the discussion about
conservation of horological objects but is not definitive.

If the clock is to function, the following items need to be
considered: Using a 10,000 year view point as a measuring stick,
consider the following:

Rarity

If the clock is one example of a design of some very low
production number, even if the maker is not well known, then it
needs to be conserved with care. The low production volume imposes a
severe limit on the amount of historical information that we have
available on this particular maker and that limit dictates, in the
case of a requirement of functionality, a replication of the
artifact.

A replication will relieve the problems associated with the
replacement and replication of worn components as well as the
disappearance of historical information. It will not, however,
relieve the costs associated with functionality: regular
maintenance, damage by handling, and wear. It will also be expensive
to make the replication.

In the case of non-functionality: the development of a careful
Conservation plan for the protection of this object is absolutely
required. Permit me to digress for a moment and express this
thought: so often we have a tendency not to protect the un-popular
makers of the day as well as we protect the popular but in the grand
scheme of things, they are all equally important.

If the clock is "one" of many (in other words, a production
clock... easily found with many other "clones" in existence), then
as long as one or two are held in "trust" somewhere on this earth,
the operation of this object along with the ramifications of
function is certainly acceptable. The difficulty here is determining
"if" any "perfect examples" are held in "trust" and if that
"trust" is irrevocable! Replication and replacement of worn
components of a "production" object deemed acceptable for use as a
functional object is a reasonable and acceptable position to hold in
this case. But, remember that the supply of production clocks or
watches is dwindling with no replacements in sight!

Loss of Historical Information

Historical information can be lost in many ways such as:
handling, cleaning methods, exposure to UV, wear, and treatment
techniques. But, what is the historical information that we are
losing?

Some historical information can help us to identify and
understand the materials that were used as well as to contribute to
the larger picture of where these materials fit into a countries
socio-economic development. Likewise, determination of how these
materials were manufactured and used can also point to information
about a countries economic and technological growth. Thus it is
important to determine if the metal was hammered or rolled or cast
or filed or machined or produced using cost reduced methods (such as
is being done today). Replacement of components within an object may
not totally compromise the historical worth of the object in the
larger sense but will render interpretation more difficult in the
future. If the object is a "one" of a kind, then the impact from
repairs is significant: if the object is "one" of many, then the
impact is lessened. Cleaning can affect ability to track an object
from its generation to its present location: various "dirt" or
"salt" deposits can provide precious clues to an objects past but
to some observers can be visually unbearable. Cleaning can erase
clues about the environment in which the clock or watch has existed.
And, without documentation prior to any treatment, we've lost it
all!

Wear

In all cases of functionality (this can be applied to all manner
of functional objects such as airplanes or trains or machine tools,
etc), wear is going to take place: wear of the bearings (or bushings
if the bearings have already been replaced), wear of the pivots that
rotate in the bearings and wear of the sliding components such as
the escapement pallets along with their respective escape wheel
teeth, wear of the conjugate surfaces of the striking and chiming
levers, and wear of surfaces of the gear teeth that are in contact
with one another. In fact, all wear is caused by sliding one surface
over another be it sliding or rotating.

Consider, for a moment, the motion of a shaft in the "Time"
portion of the clock or watch: each time the clock "ticks" the shaft
will perform the following actions: "stop", "roll ahead", "stop",
"backup" ( if the escapement is a "recoil" escapement), "stop", and
then repeat the sequence over and over. When the shaft "rolls ahead"
it tends to climb up on a wave of lubrication: when it comes to a
"stop", it sinks down through that wave to rest very close to the
bearing wall. The "dwell" time or "stop" time is dependent upon the
escapement design but it can be sufficient to allow the shaft to
settle down so close to the bearing wall that it is possible to
catch a high spot of material and the next time it "rolls ahead", it
will displace that high spot of material from the bearing wall: this
is a form of wear.

Consider, for a moment, the motion of a shaft in the "quarter
chiming" gear train: those shafts rest in one position for almost 10
minutes... plenty of time for the pivot to approach the bearing
wall: far more time that then "time" train has. This resting period
can cause more wear in this train than in the "time" train if
allowed to cycle an equivalent amount as the "Time" train.

Consider, for another moment, the motion of the shaft in the
"hour striking" train... it rests in one position for almost 50
minutes: far more "resting" time than either of the other gear
trains and far more potential to produce wear as a result of
penetrating the barrier layer of lubrication prior to motion.

Airborne Abrasives

Now, consider, for a moment, the introduction of airborne
abrasive particulate and what would happen if a particle interjected
itself between the pivot/bearing interface. Because the bearing
material is usually softer than the pivot material and the abrasive
particle larger than the irregularities of either surface, the
abrasive particle will become imbedded into the bearing wall and act
as a piece of "sandpaper" or as a "lap" and cause wear to occur on a
regular basis. If the lubrication is renewed without the pivots
being polished or the bearings being replaced, the wear will occur
faster because the abrasive particle's cutting edges will be kept
clean by the lubrication. (This is sometimes evidenced when a clock
has been run for a very long time without maintenance and then is
just "cleaned": it usually will not run reliably after the
"cleaning". This is because the bed of gunk that has covered the
abrasive particle was removed during the cleaning process. Now, not
only is the particle removing materials rapidly from the pivot but
the pivot and bearing are worn and don't fit together as well as
they did before the wear occurred.)

Wear can take place from a variety of reasons in addition to the
above noted ones. Wear can occur as the result of gears engaging
with one another and applying a pressure to the rotating pivots
causing the bearings to wear in one direction. Wear can occur as a
result of lubrication that has failed. Wear can occur as a result of
a corrosive atmosphere. And so it goes.

Lubrication

Part of the key to reduced wear is the type of lubricant that is
used: not all clock or watch lubricants are created equal! What is
needed is a long chain polar lubricant: one that can lay molecular
chains of lubrication between the interface of the pivot and the
bearing wall and have one end of that chain "attached" to either the
bearing wall or the pivot. The same holds true for any other sliding
components. But, this lubrication is not a total solution and it
never will be. Lubrication will not prevent wear: it will only slow
it down. At the atomic or crystalline level, it is impossible to
completely separate the sliding surfaces. Clock and watch
lubrication is not pressurized so the components are not always
floating on a surface of lubrication and in the long run,
pressurized lubrication will not prevent wear either.

A common mistake is oiling the clock or watch without proper
cleaning or the addition of new lubrication to the old. Not only is
there a very good chance of an unwanted chemical reaction between
the two lubricants but the lubricating qualities of the new
lubrication will be negated or degraded by the presence of the old
lubrication's compromised components. Another result of adding
lubrication is that the clock is allowed to function far beyond a
reasonable maintenance period and this will cause severe wear to
occur.

The older lubrications were made from sperm whales or porpoises
and contain various acids as well as organic components: one will
lead to corrosion of the metals and the other to decomposition of
the lubricant.

Environment (Including Visitors)

As you can imagine, the welfare of the object is subject to its
environment also! Having a stable temperature and relative humidity
can play a large role in preventing surface corrosion and the
development of micro-climates within the mechanism. The volume of
visitors and the frequency of the fluctuation of temperature and RH
as well as the number of particulate generating objects in the
vicinity such as rugs and open windows will drastically affect the
MTBT (mean time between treatments) and a short MTBT can be an
expensive proposition.

A MAJOR PROBLEM: Who is qualified to conserve a clock
mechanism?

Not all clock repair people are created equal: not all have the
same training nor background nor the interest in preservation. There
are very few trained horological conservators in the world but there
are hundreds of local repair people. Most of these people either
learned this trade by using text books with techniques that can be
very damaging to an object or they apprenticed under someone who
used those texts. Very few of the local clock repair people have a
detailed understanding of the mechanics of horological objects let
alone the understanding to use techniques that would be harmless to
the object. There are some schools that produce very well trained
and informed students in the mechanical aspects of horological
mechanisms such as the British Horological Institute (BHI) but they
do NOT teach conservation techniques or philosophy and they still
use the same text books with the same techniques that can be
damaging to an historical object. Other schools have attempted to
teach the conservation of horological objects but have not been very
successful at this point.

The best candidate of all as a horological conservator would be a
person "program trained" in conservation and who has attended the
BHI. or the WOSTEP program (Watchmakers of Switzerland Training and
Educational Program). There are no serious 2 or 4 year horological
schools in the United States as of this date ( there are some
evening classes and a couple of schools for hobbyists).

Conservation is an attitude: they may have the best training in
the world but not have a conservation view point or attitude or
values and those are the most important ingredients.

So, how do you judge if the local repair person is capable of
"conserving" your clock? Of necessity, you need to know something
about the appropriate conservation techniques used to conserve a
clock, you need to know the person's source of education, you need
to know something about the mechanism, and the mechanical techniques
used for the "repair" of them: you cannot rely on the
recommendations of others in your field. Regardless, closely
monitoring of the treatments while they are happening is absolutely
necessary when hiring outside contractors: their motivation is money
and yours is preservation and usually the twain never meet.

In addition, it has been my experience that detailed past
treatment documentation is at best scanty or non-existent. You must
demand and receive documentation on all of the chemicals used for
cleaning, the names of the coatings used if any, the manufacturer of
the lubrication as well as its description and the chemical
analysis, a "before" and "after" report of the bearings replaced,
the pivots polished, and the components replicated as well as any
adjustments that were made. There must be no secrets!

To help you understand a small amount about the conservation of
functional clocks, I am providing you with some conservation view
points as well as some information about some repair techniques. The
following information is not a full fledged treatise on the subject
but it will be enough to help you. Also, be sure to use the
references that I have provided to you at the end. Just a note: the
conservation of non-functional clocks is different; it is less
invasive.

Bearing Techniques

Bearings are holes in the front and rear plates of a clock
movement into which the ends of the shafts (called pivots) are
placed. The purpose of a bearing is to locate accurately the
position of the shaft. Accurate location of a pair of shafts insures
that the proper placement of their respective gears and insures
efficient transmission of the available power. As the bearings wear,
the distance between the gears increase and causes the transmission
of power to become more inefficient and at the same time increases
the wear of the gear teeth, pivots, and bearing walls.

When bearings need to be replaced, no more material should be
removed than is necessary to retain the new bushing safely and to
provide proper centering. It is usually necessary to file out the
worn bearing hole until the hole is once again centered about the
original center location. If at all possible, removal of material
should not exceed the diameter of the original oil sink. The use of
pre-manufactured bushings (readily available from suppliers) that
are not of the proper length must be avoided because the length of
the journals will be too short to support the loads imposed upon
them. On the other hand, the use of pre-manufactured bushings that
are too long is also inappropriate because , in time and through
wear, they will effectively eliminate the end-shake necessary to
allow the shaft to rotate freely. Stacking pre-manufactured bushings
to make up for the lack of journal length must be avoided as the
join between the two bushings will provide a place for abrasives to
gather. It is best to make bushings to fit that to try to make do
with what is on hand. When making bushings, one must make sure that
the alloy is known and that information is contained in the
documentation for the clock or watch.

When a bushing has been installed, the oil sink should match the
shape and depth of the original but should not be blended to the
point of being unable to be identified as a replacement. If at all
possible, the bearing material should be of a slightly different
mixture of the same alloy type so that in the future ready
identification can be done with an SEM or visually.

Oil Sinks

Oil sinks are concave hemispherical cavities that surround the
end of the bearing and are located on the outside of either the
front or rear plates. Their purpose is to hold and prevent the
spread of the clock lubrication that is applied to the bearing. Most
people apply far too much lubrication to a clock or watch pivot and
this usually causes the lubrication to run out of the bearing and by
capillary action will cause the bearing to go dry. The proper amount
of lubrication is when a micro-meniscus forms between the pivot
shaft and the base of the oil sink.

Cleaning Techniques

Unlike a painting or a sculpture that can have its surface
"easily" cleaned, a clock movement has to be completely
disassembled, then cleaned of surface accretions, and then
re-assembled (usually it is not as simple as this although we all
wish it were so!). Clock movements can consist of up to 500
individual components and each component has a series of surfaces
that need to be cleaned. Effective and safe cleaning cannot be done
by the "dip and swish" method! And, cleaning should not be
done using an ultrasonic cleaner: it must be done by hand.

The preferred cleaning solution used by most clock repairers is
an aqueous ammoniated cleaner either pre-manufactured or home-made.
In any case, exposing stressed brass ( most clock components contain
stresses) to ammoniated cleaning solutions will produce a known and
verifiable effect: Stress Corrosion Cracking (SCC). SCC may not
happen instantaneously but it will happen and it is not reversible.
Some repairers use a pre-manufactured "non-ammoniated" cleaner but
instead of ammonia, it contains one of the following relatives of
ammonia: "mono" or "di" or "tri" ethanolamine. These
particular chemicals are also capable (an have been documented as
causing) of producing SCC. This means that you have to insure
that your object is cleaned in a manner that is harmless to your
object. (Ref: Ammoniated cleaning solutions by James Moss: American
Horological Times, Volume 22, Number 2, February 1998; British
Horological Journal, Volume 139, Number 8 .)

For cleaning a clock movement, I presently use hydrocarbons and
alcohols in combination with manual labor, fine brass and steel
brushes (only occasionally), stiff bristle non-metallic brushes (all
of the time) and sharpened pieces of wood called peg wood: I do not
use an ultrasonic. If steel brushes need to be used, they should
only be used on steel components: likewise brass brushes should only
be used on brass components because if a brass brush is used on a
steel surface, corrosion cells can be set up and over the long term
and in the right conditions, corrosion can take place. Restricted
use of the metallic brushes is necessary as they will remove any
protective oxide layers even with careful use.

Pivot Polishing

The purpose of the pivot is to work in conjunction with the
bearing to locate accurately the position of its related shaft. Each
shaft has two pivots: one on either end. As stated in a prior
paragraph, accurate location of a pair of shafts insures that the
proper placement of their respective gears and insures efficient
transmission of the available power. The pivots must be polished to
a mirror finish (they will appear to be black if properly polished)
and usually, but not always, they are cylindrical and have parallel
sides. A polish less than mirror like will produce wear as it is
actually a miniature rotary file!

Replication

If a component is damaged or worn to the point that simple
polishing will not allow it to work properly, then the entire
component needs to be replicated. This means that if there is a gear
that is too damaged to work properly, then the gear and its shaft
and any other of the assembly's associated components need to be
replicated and the original assembly needs to be stored safely. You
should be able to substitute either assembly into the mechanism
without any additional work, and the clock should work properly
(assuming that the part needing replication was complete and whole).
Replication of only part of an assembly many times can cause more
damage to the overall assembly during the process than is necessary.
Replications should be made of material similar in composition as
the original but sufficiently different that analysis can easily
determine the difference between the original and the replication.
All replications must be signed and dated and labeled as a
replication.

Maintenance Period

Because the preservation of a functional object is paramount,
cleanliness is one of the major keys to longevity. This means that
frequent cleaning of the clock movement is imperative. From a long
term preservation standpoint, the MTBT of once every year would not
be unusual and would be recommended: a MTBT once every two years
would be approaching the "too infrequent" mark.

Coatings

Under normal circumstances, clock and watch components in
functional objects should not be coated as there is a possibility
that the lubricants used could react adversely with the coatings.
Brass has a naturally occurring oxide that will cover the brass
surfaces with a perfect "non-holiday" coating and is the best that
nature has to offer. Coatings applied by spray gun or human beings
are fallible and need to be replaced approximately once every 20-25
years under the best of conditions. By utilizing the oxide coating
the brass, the process of removal, preparation, and re-application
of an organic coating is one more intervention that will not be
needed and one less chance for damage to the object.

Techniques to Correct for Wear

Many times, in an effort to retain historical information, a person
will move the position of a component to an unworn section of its
conjugate component. After a few moves such as this, there will be a
permanent loss of information about the method of manufacture of that
component: in the interest of the preservation of historical information,
it would be better that the entire assembly be replicated and the original
assembly be saved with the one spot of wear than to "fix" that one spot
by repositioning components.

Handling

Winding the clock, setting its hands and the various dials, as
well as moving the clock can expose the object to serious damage.
Always consult with a responsible horological conservator for proper
instructions concerning these actions before performing them. There
are many variations and there are no absolute rules regarding the
above processes.

Non-Functional Clocks and Watches

Even if you choose not to run the clock, this decision does not
abdicate the necessity for preventative conservation and
stabilization. Surface accretions, coagulated lubrication and
lubrication that contains an acidic component, as well as other
contaminants need to be removed from the interior and exterior
surfaces of the mechanism. Protection from corrosion needs to be
provided. Coatings need to be carefully determined before
application.

References:

"Ammoniated cleaning solutions" by James Moss: American
Horological Times, Volume 22, Number 2, February 1998;
British Horological Journal, Volume 139, Number 8 .